This invention relates generally to the field of printing and, more particularly, relates to a method and a printing device for use in the production or printing products.
In the prior art, the carrying out of a plurality of print jobs following one after another, in particular in the case of sheet-fed, offset printing machines, is predominantly controlled in accordance with purely operational and economic or time aspects. The individual print jobs are allocated to one or more printing machines in accordance with a given priority in order to achieve the highest possible machine utilization, and the print jobs are then processed one after another on the printing machine or machines. A job change from one just carried out to the next print job typically requires, in the case of a sheet-fed, offset printing machine, essentially the changing of the printing plates as well as the possible changing of the printing inks present in the individual printing units and the material to be printed in the feeder. The corresponding devices, in particular for supplying the material to be printed in the feeder and deliverer, must at the same time be set appropriately as a function of the job. In the case of modern sheet-fed offset printing machines, this takes place automatically by means of remotely adjustable devices whereby the changeover times for a job change can be shortened.
For example, DE 37 07 695 C2 discloses a method for the defined distribution of ink in the inking unit of rotary printing machines for setting up an ink gradient which allows the unit to achieve close to continuous printing. This is achieved by changing ink metering elements in a targeted manner during a job change, starting from an initial position, and taking into account the setting envisaged in the case of the next job. By this means, the number of machine revolutions over which the ink gradient is then established on the rolls of the inking unit is minimized. This method is used in connection with an already defined sequence of print jobs.
By way of further example, EP 0 453 855 B1 discloses a method for the elimination and for the reconstruction of an ink profile of the inking unit of an offset, rotary printing machine. Provision is made for the complete inking of the printing form by throwing off the damping solution feed in order to equalize the previous ink profile which has been brought about by the previous print job. The ink profile originating from the previous print job is thereby reduced to an envisaged minimum film thickness so that the result is a shortening of the time interval between the changeover from one print job to the next print job. Again, this method is used in connection with an already defined sequence of print jobs.
As yet another example, DE 44 45 393 A1 discloses a copying and/or printing device in which a so-called buffer store is provided which, in order to carry out appropriately prioritized print jobs as rapidly as possible, can be changed over from a first-in/first-out sequence into a first-in/last-in sequence. Accordingly, in the first mentioned mode of operation, print jobs following one another are carried out in the sequence in which they were written into the buffer store. A print job which is marked with an appropriate priority effects the above described sequence changing the sequence into the first-in/last out sequence, with the result that this print job can be carried out immediately or as rapidly as possible. In the case of this device, although there is flexibility with respect to the execution sequence of successive print jobs, the printing is performed using an already defined allocation of priorities.
As a yet further example, DE 31 28 360 C2 discloses a matrix printer which is equipped in such a way that, using one and the same printer, two or more different printed documents can be produced. To this end, the printer has a printing buffer store, an input buffer store and a sorting store, so that the information which is downloaded to the device is separated and sorted in such a way that the individual information blocks are printed onto the printed documents in any desired sequence and arrangement.
Nowadays, increasing use is being made of printing machines having electronically writable or rewritable printing forms. Such digital printing machines, by means of which a so-called digital changeover can be carried out, are employed particularly when low issue levels are to be produced in the shortest time. However, short-run printing devices need high utilization with respect to the printing time for their practical use in order to be able to be employed profitably. Depending on the principle used for the writing or rewriting of the printing forms, specific minimum times between two print jobs have to be provided. As in the case of conventional printing machines, a complete rewriting of a printing form with the entire image content is performed in accordance with the print job to be carried out at that time. This has the effect that, during a job change from an existing to the next print job, the previous image contents have to be erased (for example by means of a specific image cleaning device) in order then to provide the printing forms or the corresponding cylinders with the image contents of the new print job. The term "writing image information" onto a printing form or onto a printing form cylinder is to be understood here and below as any generation or structuring of parts, in particular, ink-carrying/ink-accepting and non-ink-carrying/non-ink-accepting parts.
In particular, writing to a printing form typically requires, for example, in the flat printing process, producing the ink-accepting regions corresponding to the structure envisaged for the print by means of electrical, thermal, mechanical or optical treatment of a starting material. Before a subsequent image is printed, a so-called erasure of the printing forms takes place. This erasure occurs in a similar manner with the image content being transferred once more into an initial state, for example, by means of full-area thermal, mechanical, electrical or optical action on the appropriate substrate. The writing step is then performed in order to generate a new printing form having the image content for the next print job. The processing operations outlined using the example of a rewritable flat printing form are to be carried out appropriately in an analogous way in the case of a process designed as a rewritable gravure process. The writing of the printing form utilizing this process essentially comprises a generation of tiny bowls of designed depth in accordance with the image information to be transferred during the printing. The erasure of the printing form accordingly comprises refilling all the little bowls of the previous print job.
While each of these above described examples work for their intended purpose, there is seen to be a need for a still more efficient method and device for use in the production of printing products.